1. Field of the Invention
The present invention relates to an Electromagnetic Bandgap (EBG) structure, and more particularly, to a resonator and a bandpass filter having an overlay Electromagnetic Bandgap (EBG) structure, and a method of manufacturing the resonator.
2. Description of the Related Art
Recently, many communication equipments are becoming lighter and smaller according to customer demands requiring portability. In order to manufacture communication equipments smaller, high frequency bandwidths have to be used. When high frequency bandwidths are used, the size reduction of communication equipments is possible and also a large amount of communication channels is available.
A communication equipment essentially requires a function of selecting or controlling a specific frequency. In order to implement the function, generally, a communication equipment includes a circuit structure of selecting or controlling a specific frequency. The circuit structure may be a resonator, a filter, etc.
The circuit structure, such as a resonator or filter, for selecting and controlling a frequency may be implemented by arranging lumped type passive elements (for example, inductors, capacitors).
However, when a resonator or a filter is manufactured having general passive elements, the resonator or filter may perform undesired operation at a high frequency. That is, if a wavelength is shortened at a high frequency, interrupt between communication lines becomes significant. In the case of a general passive element, since such interrupt between communication lines increases unexpected factors, the general passive element may not properly operate at a high frequency bandwidth (or at a millimeter wave bandwidth).
A representative study on development of a passive element capable of operating at a high frequency bandwidth is to integrate existing lumped elements on a plane and estimate parasitic components in a high frequency environment.
Another study on development of a passive element capable of operating at a high frequency bandwidth is to use an electromagnetic band gap (EBG) structure in which a photonic band gap (PBG) structure for guiding photons is applied in a high frequency area. Such an EBG structure is applied to resonators, filters, etc. of various small-sized communication devices, because the EBG structure is suitable to package a high frequency circuit.